Quantitative Analysis of DEPES Distributions of Pt(111)

K. Kruk, I. Morawski Institute of Experimental Physics, University of Wrocław pl. M. Borna 9, 50-204 Wrocław, Poland

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Directional elastic peak electron spectroscopy (DEPES) was used to reveal a short range order within the near-surface region of Pt(111). Experiments were performed at primary electron beam energies in the range from 0.9 keV to 1.8 keV. DEPES signal was recorded for a wide range of polar θ and azimuthal ϕ angles and then transformed to two-dimensional DEPES maps using stereographic projection. Theoretical DEPES distributions were obtained with the application of the multiple scattering (MS) theory. In MS calculations, the following parameters were varied: the inelastic mean free path λ, the radius around the emitter Rmax and the cones of smoothing M. The comparison of experimental and theoretical DEPES maps was performed by an R-factor analysis in order to find the best correspondence between the recorded and calculated distributions. The absolute minimum of the R-factor was found at rather small values of the radius around the emitter and large inelastic mean free paths. However, the obtained minimum was very shallow and took the form of a characteristic band in the Rmax(l) plots. Thus, other Rmax and λ values corresponding to the local R-factor minimum can also be to some extent used in computations. The cone of smoothing, which reflects the spread of primary beam directions before it strikes the sample, decreases at larger electron energies which scales with better electron focusing at larger Ep values. The discussion concerns the computation time associated with the mentioned parameters and the convergence of theoretical data.

DOI:10.12693/APhysPolA.138.459 topics: retarding field analyser (RFA), directional elastic peak electron spectroscopy (DEPES), crystalline structure, short range order, scattering of primary electrons